Research On Floating Raft System With Self-adaptive Feed-forward Control

Submarine main noise contains mechanical noise, hydrodynamic noise and propeller noise.When the submarine is crewing in the low speed, the main noise is from the running machine inthe submarine. Floating raft system is a widely-used isolation set for vibration and noisereduction. However it has a disadvantage to depress low frequency vibration. And activevibration control(AVC) is an effective way for reducing the vibration of power plant at lowfrequency. To improve the isolation performance of the conventional floating raft system, activedynamic vibration absorbers (AVAs) were applied in this article. The multi-channel self-adaptivefeed forward law based on filtered x-LMS algorithm was designed for the floating raft systemwith AVAs and simulated to test its control effects.Firstly, the rationale of single-layer vibration isolation system and double-layer vibrationisolation system was analyzed. To depress low frequency vibration, active vibration controltechnology was applied additionally. Displacement feedback algorithm, velocity feedbackalgorithm and acceleration feedback algorithm were researched. And further study andsimulation of double-layer vibration isolation system with AVAs based on PID feedbackalgorithm were executed.Secondly, a floating raft system with AVAs was presented, using the sub system mobilitymethod. The transfer functions of disturbance channel and control channel were obtained andtheir amplitude-frequency curves were also analyzed.Thirdly, the single-channel self-adaptive feed forward law based on LMS algorithm wasstudied. And considering the filtering function of control channel, the single-channelself-adaptive feed forward law based on filtered x-LMS algorithm was proposed and simulated.Finally, an evaluation function about reducing the sum of mean square error of vibrationresponse of four observation points which were located on the flexible foundation of floating raftsystem with AVAs was formatted.With this objective function and based on filtered x-LMSalgorithm, the multi-channel self-adaptive feed forward law for the floating raft system withAVAs was designed and simulated.The simulation result shows that it’s effective to use thefloating raft system with AVAs for reducing the vibration of mechanical device at low frequency.